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Am I doing something wrong???

PostPosted: Fri Mar 28, 2014 4:33 am
by Max Normandin
Hi guys

First, here's my setup: BMCC MFT, Prores, Speedbooster (always on), Rokinon Cine Lenses.

I'm shooting daily and noticing some inconsistencies in the quality of the footage. For instance, yesterday we shot some pretty awesome footage using Rokinon's 24mm w/ Speedbooster at 4.5f.

Today, I'm shooting in broad day light, closed all the way down, with speedbooster and a nice filter on top of that. I'm thinking, ''shooting closed all the way down, the image quality and sharpness should be great''.

i'm uploading the footage on my computer today and the image is grainy, with a lack of definition.

This happens to me every now and again. What am I doing wrong? Are the Rokinon cine lenses somehow LESS sharp when all the way CLOSED???

I'm at a loss here...


Thanks for any help, suggestions.

Max

Re: Am I doing something wrong???

PostPosted: Fri Mar 28, 2014 4:48 am
by AdrianSierkowski
All leneses perform best in the middle of their range. On the extremes the image quality suffers considerably, hence why most DoPs try to aim for a 4/5.6 but will shoot if they can from aound a 2.8 to a 8, depending on the lens.

My own Super Speed 9.5mm for example, looks HORRIBLE at a T1.3, and looks mildly ok at a 4, and then looks like my god, what is this at an 11.

Re: Am I doing something wrong???

PostPosted: Fri Mar 28, 2014 6:18 am
by Dustin Boswell
What ASA (ISO) did you shoot at?
How bright was the day? (If it was cloudy it could be that you stopped down a bit too far and caused noise to form)
and when you are looking at the footage are you looking at it in full res or on a minimum 1080p monitor?

I notice when I look at footage on my laptop (1440x900) It tends to look grainy and weird, but if I view it on my nice full 1080P Monitor on my PC it looks normal.

Also, what Adrian Said.

Re: Am I doing something wrong???

PostPosted: Fri Mar 28, 2014 7:20 am
by Mac Jaeger
Max Normandin wrote:... and a nice filter on top of that ...

What kind of filter? The BMD cameras are rather sensitive to infrared light - so if you had an ND-filter mounted, make sure you also add an IR-filter, otherwise you loose contrast and may end up with redish shadows and color casts in dark areas.

Adding to that i can only agree to what has been stated already: most lenses perform best around f/4 to f/8, stopping down further will usually lead to less sharpness, less contrast, due to refraction. That's why ND filters are so important, especially when shooting at (native) ISO 800.

Re: Am I doing something wrong???

PostPosted: Sun Mar 30, 2014 11:28 pm
by Brad Ballew
Yeah don't close all the way down. I have several Rokinon lenses and for most of them, if you get to the mid to high teens then your footage will look pretty crappy. Someone explained to me why that is, but I forgot the specifics. It has to do with how the light moves around in the lens when it closed down all the way. Perhaps it is bouncing around a little too much giving it a hazy look?

Re: Am I doing something wrong???

PostPosted: Sun Mar 30, 2014 11:30 pm
by AdrianSierkowski
That's part of it; but generally reflective errors are from wide open lenses. What you have is the light bending and being refracted by the iris.

Re: Am I doing something wrong???

PostPosted: Mon Mar 31, 2014 8:33 pm
by RB3tv
Thanks for the advice and information about this from everyone who posted. Much appreciated.

Re: Am I doing something wrong???

PostPosted: Mon Mar 31, 2014 8:56 pm
by Craig Marshall
The Rokinon is a cheap lens so you get what you pay for. Wide open and closed down, it is very soft so try to shoot at the lens sweet spot. See this comparison. Even with internet compression, the results speak for themselves: